1. Field
This disclosure is concerned generally with the field of blood bags made from flexible polymeric materials and specifically with a blood bag and blood bag label combination which provides increased gas transmissibility for the blood bag.
2. Prior Art
Blood and blood components are commonly collected, processed, stored and administered in containers simply referred to as blood bags or blood bag systems. These are made from a flexible polymeric film which should be of a medically acceptable quality. The bags may exist as single bags having various access ports or multiple bags comprising two or more otherwise single bags in closed communication with one another via appropriate tubings which may include various valves or temporary seals. In the case of multiple blood bags, there are typically a so-called donor bag (or primary bag) into which whole blood is collected via attached tubing and attached donor needle and various satellite bags (or secondary bags). Into these various components or sub-components of whole blood may be expressed via connecting tubing after they have been separated (usually via centrifugation) in an attached bag, typically the donor bag or an additional satellite bag.
The above bags are commonly made from films of polyolefins, polyolefin mixtures, or polyvinyl chloride plasticized with plasticizers known in the art as di-2-ethylhexyl phthalate (DEHP or DOP) or, in some cases certain triesters of trimellitic acid such as tri-2-ethylhexyl trimellitate (TOTM or TEHTM). These films and the above PVC plasticizers are described more fully, for example, in U.S. Pat. No. 4,280,497 to W. Warner et al and U.S. Pat. No. 4,222,379 to D. Smith, the teachings of both being incorporated herein by reference.
It is known that certain blood components (particularly platelets) require an exchange of CO.sub.2 and O.sub.2 through the plastic collection bag during storage to remain viable. See, for example, U.S. Pat. No. 4,280,497 to Warner et al, cited above, and the publications cited therein. It has been found, for example, that when platelets are stored in a TOTM-plasticized PVC blood bag or certain polyolefin bags, a greater degree of gas transmissibility is possible. This greater gas transmissibility in turn permits better platelet storage properties (e.g. 5 days storage vs. 3 days), a desirable property.
Conventional blood banking practices require a relatively large (3".times.4" or 4".times.4") paper label be securely attached to the bag throughout the preparation, storage, and administration of a unit of blood or a blood component. This label may cover up to one fourth of the bag surface and, unfortunately, it has been found that the label may significantly reduce the amount of gas diffusion through the bag/label structure, thus, in some cases, impairing component viability.
Currently, paper labels are attached to a blood bag in either of two ways:
1. The more common heat seal method employs a heated platen which, with heat and pressure, melts the adhesive backing of the label and presses it into the bag film. About 100% of the inner label surface is then firmly attached to the bag.
2. A second method uses a label with a pressure sensitive adhesive backing which requires only pressure to attach it to the bag. A disadvantage of this method is that the label is not as firmly attached to the bag as with the heat seal method noted above. Accordingly, it is a preferred practice to use the above heat seal method for label attachment even though, because of its size and attachment, it interferes with gas diffusion through the bag.
Quite surprisingly, we have devised a blood bag-label combination which enhances or maximizes gas transmissibility while still permitting the label to be firmly affixed or attached via thermoplastic adhesive to the bag throughout common blood banking procedures. Details of our invention are disclosed below.